From Rigtacular Enterprises:
Welcome to Eureka!
This screen saver features a Multi-Ground system, so it contains multiple backgrounds and foregrounds. The only rule is that you cannot activate more than 1 background; doing so creates display glitches and a very odd picture.
Accessing the controls for this screen saver can be done by clicking the "options" button in the Desktop & Screensaver preference pane in System Preferences.
This is a spotlight that scans back and forth accross the Tiger (10.4) Aqua desktop wallpaper. It is pretty cool to look at, and makes for a good background for the foregrounds.
This requires an iSight; all new and previous generation macs (except for Mac Pro) have these built in so it is of no worry to most users. This background mimics a full screen "reflection" of the area in front of the computer via the iSight camera.
This is exactly what it says. This scans your pictures folder, in particular your iPhoto Library, and makes a slideshow of the pictures it finds. Nothing too special here.
This is the iconic foreground of Eureka!. It features a spinning, moving array of pictures from your iPhoto Library. It cycles through the pictures, so you always have something fresh to look at.
This is exactly what it says; it's a bit of text that pulses on top of everything else with whatever message you want to show. Pretty useful sometimes.
This requires an internet connection; although it is fully customizable, it will by default show the hot news from apple.com. This mimics the RSS Visulaizer screen saver included with Mac OS 10.4 Tiger, but does so in a clean, look-good-on-anything way. to use the hotkey shortcuts, you must have Safari selected as your default web browser.
This borrows the RSS Feed foreground and uses it to check the RigTacular website for any updates to Eureka!.
This feature uses numerous settings built into Eureka! to dumb down or boost up the graphics; in essence this allows users with older machines to improve performance, and users with newer machines to max-out quality.
Eureka! v1.5 is on the way, with several improvements and additions.